Buoy Operations: Recovery

10/29/08

Most of the instruments that are deployed either on an open-ocean buoy or on the mooring line are unable to transmit their data to shore via satellite phone. They have to store their data on internal memory cards. As a result, if you want to collect the data from those instruments you have to recover the buoy and the mooring line, disassemble the instruments, and extract the memory cards. Now, the buoys that you recover have usually spent a year or more in open waters with only birds and aquatic life to keep them company. In fact, many sea critters decide to call the buoy and it's mooring home. After a year at sea, the buoy and mooring line harbor their own ecosystem. Read on to see what I mean.

Follow up:

Recovering a buoy follows the same process and deploying a buoy, just in reverse. To start the recovery process, the ship sends out an acoustic pulse deep into the water that triggers the acoustic release. Once triggered the acoustic release lets go of the anchor chain and the glass balls at the end of the mooring line float the end of the mooring line to the surface of the water. If you recall from the pictures in my previous post, the glass balls are housed in a bright yellow shell so that the cluster of floating balls can be easily spotted on the surface of the ocean. Once the floating glass balls are spotted, the ship moves alongside them so that they can be grabbed and hoisted onto the ship and the attached mooring line can be secured.

The Ronald Brown plucks the glass balls from the ocean and secures the mooring line

Despite the fact that the glass balls were attached to the mooring in a nice orderly fashion, between floating to the surface through 4500 meters of water and being pulled onto ship with a wench, they're little more than a big tangled knot when they're placed onto the deck. Once they are on deck, the recovery team descends onto the pile to disassemble the tangled mess and get the glass balls cleared out of the way. The glass balls are assembled in strands of four and the fasteners are held in place with a threaded bolt with a cotter pin. The cotter pins are removed, the fasteners are undone, and the glass balls are hauled out of the way a single strand of four at a time. One of the glass balls apparently couldn't handle the deep sea pressure and exploded. Its housing was torn to shreds. All that was left was a twisted knot of jagged plastic. One of the observers from the Chilean government was helping with the recovery and sliced is palm on a shard of the glass earning him five stitches. I have to give the guy credit however. He was back to work within the hour, bandaged hand and all.

The recovery team acts quickly to sort out the tangle of glass balls

After the glass balls are secured, the next step involved reeling in roughly two miles of synthetic rope. Doing so involves and upright wench and a team of two to feed the rope into a series of three large boxes. Pulling in all the rope takes a while so different poeple take turns feeding rope into the boxes.

Jeff Lord, overseer of buoy operations, feeds rope into a box

Like I said above, they whole recovery process is just the deployment process backwards. So, once the rope was in, we started recovering cable and instruments. This is where the fun begins. While the instruments and buoy went into the water shiny and new, they come out of the water teeming with life. In their ocean observing tenure, they've become habitats for the indigenous fauna. The technical term for this is biofouling as the various critters can impair the functionality of the instruments.

Closeup of a critter that grew on a sensor

Instruments become home to a cornucopia of life, mainly filter feeders

Before the data can be recovered from the instruments, they have to be cleaned and sorted. This is a messy and smelly job and every free hand on the ship is conscripted into service.

Instruments are carefully scraped free of ocean critters

Finally, the buoy, along with the last 50 or so meters of mooring chain, is plucked from the sea via crane so that it too can be cleaned. You never really think about what can grow on something that sits out in the middle of the ocean. Tens of thousands of creatures attached themselves to bare metal surfaces where they live and grow. They say a rolling stone gathers no moss, but a floating and continually moving buoy gathers plenty of aquatic life.

The buoy, still teeming with life, on deck after recovery
Photo Credit: Mingxi Yang

A close up of the buoy and the cleaning to be done
Photo Credit: Mingxi Yang